1. Field of the Invention
The present invention relates to a drive power transmission mechanism for a motor vehicle, and more particularly to a drive power transmission mechanism for transmitting the drive power from a motor vehicle engine through a propeller shaft and a final speed reducer to drive road wheels.
2. Description of the Relevant Art
There are known motor vehicles in which the drive power from the engine is transmitted to drive road wheels through a drive power transmission mechanism that comprises a propeller shaft and a final speed reducer. The final speed reducer incorporates therein a limited-slip differential or a transmission for improving running performance, particularly turning performance, of the motor vehicle.
In the drive power transmission mechanism, the propeller shaft and the final speed reducer are operatively coupled to each other by bevel gears fixed respectively to the propeller shaft and the final speed reducer. The propeller shaft is subjected to positional limitations because the bottom of the motor vehicle body is required to have a certain minimum height from the ground and the propeller shaft must not interfere with a fuel tank and other components. For this reason, the axes of the bevel gears on the propeller shaft and the final speed reducer cannot be held on one plane, i.e., in alignment with each other. These bevel gears have heretofore been in the form of hyperboloidal gears such as hypoid gears meshing with each other.
Since the hyperboloidal gears are expensive, the drive power transmission mechanism is costly to manufacture. The hyperboloidal gears need a complex sealing structure since they require special highly viscous lubricating oil different from the lubricating oil contained in the final speed reducer.